Holography has a considerable advantage of retrieving three-dimensional information of an object from only one interference recording. However, twin images always appear in the reconstruction for the reason of symmetry. Especially, twin images significantly deteriorate the quality of the reconstructed information in on-axis configuration. A solution of the twin-image problem in a digital holographic microscope by using symmetry with quadrantal masks is suggested in this study. This method is effective to most of the measured area without any additional implements, and restrictions on sample or iterations, and is demonstrated by the simulation and experimental results. The ratio of the disturbed area by a twin-image to the total measured area is reduced to the value of 0.82% in a specific case.
We study the tolerance characteristic of SIAX and suggest a newly designed SIL-Axicon system for the better tolerances.
Methods for checking beam quality, optimization and remaining problems are suggested. SIL-Axicon system shows
more tolerances in the uniformity of beam incident angle. Bessel beam (BB) with SIL can be used for multi layer high
density data storage systems. We study the tolerance characteristic of SIAX and suggest a newly designed SIL-Axicon
system for the better tolerances.
Digital holography (DH) has a big advantage to retrieve the
three-dimensional (3D) information of the object from only
one interference recording. Especially, the digital holographic microscope (DHM) using a microscope objective (MO)
has been researched for 3D microscopy. The researches have progressed for compensation of aberrations and
improvement of the resolution in the optical system in recent years. Most of small aberrations caused by a MO are
compensated through various researches. However, the measured phase is distorted in the optical system, which has the
significant wavefront deformation in illuminating wave larger than number of wavelengths. In this paper, the relation
between illuminating wave and the reconstructed phase is studied based on the wave optics and the analysis is confirmed
by the simulations. The analysis of the wavefront compensation is applied to a super-resolution DHM in theory and the
technique for retrieving the distribution of the intensity and phase is demonstrated in simulation.
The digital holographic microscope (DHM) has emerged as a useful tool for verifying the three-dimensional structure of an object. A dual-type inline DHM that can be used with both transmission and reflection imaging in a single device is developed. The proper modes (between transmission and reflection imaging) can be easily changed according to the characteristics of the object in this system. The optimum condition for retrieving the correct phase information is illuminating a plane wave to an object. In contrast to the transmission imaging, it is difficult to illuminate an object using a plane wave without deformations in the reflection imaging. We developed an adequate relay lens module for illumination that can be adapted to any type of microscope objective without significant aberrations in the reflection imaging. The relationship between the illuminating condition and the measured phase based on the wave optics is analyzed. A specially designed and manufactured phase mask is observed in this system, and an alternative method for overcoming the limitation of phase unwrapping is introduced for the inspection of that object.
Axicon produces a deep focused Bessel beam whose transverse focal spot is smaller than the size of an airy disk
produced by conventional lens with the same numerical aperture. Rieko Arimoto et al. applied axicon to a beamscanning
system and established the beam-scanning imaging system which is free from need of precise positioning.
Meanwhile, the allowed amount of rotation is severely restricted due to the unwanted tilt in the focused ring. We analyze
the tilt in the focused ring quantitatively and suggest an appropriate method of designing the aberration corrected lens.
An exemplary lens design for 1° tilt in the scanning mirror is presented and it is shown that the amount of degradation is
clearly suppressed in the optimized system.
Holography has a considerable advantage to retrieve the three-dimensional (3D) information of an object from only one
interference recording. For several decades, the technology of digital holography (DH), which uses numerical
reconstruction as opposed to illuminating the reference beam to the hologram plate, has progressed with the assistance of
improvements in 2D array detectors and computers. In this paper, a dual-type inline digital hologram microscope (DHM)
system that can be used with both transmission imaging and reflection imaging in a single device is developed. The
proper method depending on the modes (transmission imaging or reflection imaging) can be changed easily in this
system according to the characteristics of the object. Illumination with a plane wave is the necessary condition for
retrieving the correct phase information. In the case of reflection imaging, unlike in transmission imaging, a special relay
lens in addition to the microscope objectives (MOs) is needed to meet the needs of this condition. However, the quality
of the 3D information can deteriorate significantly due to the overlapping twin image that is inherent in holography. This
study suggests an effective and convenient method for eliminating the twin image that is entangled in the reconstructed
information. The proposed method does not require extra components, numerical iterations, and restrictions on the
According to the ITRS roadmap, DRAM half pitch (hp) will reach to 32 and 20 nm in 2012 and 2017
respectively. However, it is difficult to make sub-40 nm node by single exposure technology with currently
available 1.35 numerical aperture (NA) ArF immersion lithography. Although it is expected to enable 32 nm hp
with either double patterning technology or extreme ultra-violet lithography, there are many problems to be
solved with cost reduction. Thus, the study of high-index fluid immersion technology should be pursued
simultaneously. ArF water immersion systems with 1.35 NA have already introduced for 40 nm hp production.
ArF immersion lithography using high-index materials is being researched for the next generation lithography.
Currently, many studies are undergoing in order to increase NA with higher index fluid and lens in immersion
technology. The combination of LuAG (n=2.14) and third-generation fluid could be used to make 1.55 NA. This
combination with 0.25 k<sub>1</sub>, 32 nm hp can be obtained by single exposure technology. In order to check the
realization of this process and to check the possible process hurdles for this high NA single exposure technology,
32 nm hp with 1:1 line and space patterning is tried. Various illumination conditions are tried to make 1:1 32 nm
hp and the exposure and develop conditions are varied to check whether this single exposure can give
processible window. As a result, 32 nm hp can be obtained by single exposure technology with 1.55 NA.